Omnidirectional orthogonal slanted dipole array

ABSTRACT

Known wide band, omni-directional, H.F. aerial system formed by two co-planar dipoles sloping downwardly and outwardly from a central twin wire feeder suffer the defect that large amounts of power are dissipated in terminating resistances at the lower ends of the dipoles. The need for the resistances is obviated by using a pair of mutually perpendicular dipoles each consisting of two co-planar half dipoles sloping downwardly and outwardly from a central feeder, the two halves of the dipoles being connected together by a length of screened cable. Insulating supports are connected between the lower ends of the half dipoles and ground.

United States Patent Nolan [451 July 25, 1972 [54] OMNIDIRECTIONAL ORTHOGONAL [56] References Cited 4 SLANTED DIPOLE ARRAY UNITED STATES PATENTS 72 Inventor: Sean i Nolan Essex, England 2,147,808 2/1939 Alford ..343/890 [73] Assignee: The Marconi Company Limited, London, Primary E mi er-Eli Lieberman England Attorney-Baldwin, Wight & Brown [22] Filed: Jan. 4, 1971 4 [57] ABSTRACT [2]] Appl T 103738 Known wide band, omni-directional, H.F. aerial system formed by two co-planar dipoles sloping downwardly and outwardly from a central twin wire feeder suffer the defect that [30] Fmfelgn Applica'mn Pnomy Dam large amounts of power are dissipated in terminating re- 1 Jan. 29, 1970 GreatBritain ..4,259/70 Sietanees a! the lower ends of the dipeles- The need for the sistances is obviated by using a pair of mutually perpendicular 52 US. Cl ..343 797, 343/890 dipoles each consisting of two ee-Pleher half dipoles sloping s1 Int.Cl. ..H01q 21/26 downwardly and outwardly from a eemrel feeder, the two 58 Field of Search ..343/734, 735, 736, 737, 73s, halves of the dipoles being nected t gether by a length of screened cable. Insulating supports are connected between the lower ends of the half dipoles and ground.

3 Claims, 2 Drawing figures OMNIDIRECTIONAL ORTHOGONAL SLANTED DIPOLE ARRAY This invention relates to aerial systems and has for its object to provide improved simple and compact wide band substantially omni-directional aerial systems suitable for use for short distance skywave I-LF. communication at frequencies of the order of 2 to 30 Mc/s.

The invention is illustrated in and explained in connection with the accompanying drawings in which FIG. 1, which is provided for purposes of explanation, shows a known aerial system and FIG. 2 is a diagrammatic representation of an embodiment of this invention.

There is a considerable demand for compact and simple wide band substantially. omni-directional aerials for short distance I-I.F. communication. Theaerial system sometimes called the -sloping wire dipole system and which is a well known form of such system, is illustrated in FIG. 1. It consists of a dipole formed of two co-planar wires D1, D2 sloping downwardly and outwardly from an upper center. The wires D1 and D2 are supported at their upper ends by suitable insulating means (not shown) from a central vertical mast (also not shown) up which is run a twin wire feeder F. The wires of this feeder are connected to the upper ends of the aerial wires D1 and D2, the outer and lower ends of which are terminated by resistances R1 R2 through which they are connected to ground. In a practical case each of these resistances has to dissipate considerable power commonly of the order of 400 watts. In practice it is common to constitute each half dipole D1 or D2 by a group of wires such as a cage of wires or a fan of wires, instead of by a simple single wire as shown, the axis of the group corresponding with that of the wire it replaces. Accordingly, in this specification, the term wire will be employed in a wide sense to include not merely a single wire but a group of wires used instead.

' The known aerial system of FIG. 1 has the serious disadvantages that relatively large amounts of power have to be dissipated by the terminating resistances and also, because of this, there is great difficulty in obtaining satisfactory robust and reliable non-inductive resistances at an acceptably low cost. The present invention seeks to avoid this and to provide improved aerial systems in which the terminating resistances R1 and R2 of FIG. 1 are eliminated.

According to this invention a substantially omni-directional high frequency aerial system comprises a pair of similar mutually perpendicular dipoles each consisting of two co-planar half dipoles sloping downwardly and outwardly from a common upper center; a feeder connected to feed one dipole at the inner upper ends of the halves thereof; and a pair of substantially non-radiating connections each connecting the outer lower end of one or other half of one dipole with the outer lower end of one or other half ofthe other dipole.

Preferably the substantially non-radiating connections are constituted by lengths of screened cable. However, it is possible to use simple unscreened connections if they are close enough to the ground to have only negligible radiation and, in many cases, it'is conveniently possible to arrange for this.

A preferred aerial structure and arrangement in accordance with this invention comprises a central vertical supporting mast carrying a feeder; four mutually perpendicular similar aerial conductors each constituting a half dipole sloping outwardly and downwardly at equal angles from a common upper center on said mast; insulating supports between the upper ends of the aerial conductors and the mast and between the lower ends of said aerial conductors and ground; means connecting the feeder to the upper ends of one pair of co-planar aerial conductors; and two screened connections each between the lower end of a different one of said one pair of aerial conductors and the lower end of one or other of the other pair of aerial conductors.

Referring to FIG. 2, the embodiment of the invention therein shown comprises two mutually perpendicular dipoles of which one consists of the sloping conductors D1 and D2 and the other of the sloping conductors SDl and SD2. The

downwardly and outwardly from their upper ends. Support at their lower and outer ends is provided by suitable insulators I which are inserted in wires anchored to the ground. The inner upper ends of the conductors SD! and SD2 are left unconnected and the inner upper ends of the conductors D1 and D2 are connected to the conductors of a feeder F which is run up the mast.

As will be seen the conductors D1 and D2 are not terminated by resistances as in FIG. 1 but, instead, their lower ends are directly connected to the lower ends of the conductors SDI and SD2 by non-radiating connections CH and CF 2. These are constituted by lengths of screened cable, one connecting the lower end of D1 to the lower end of SDI and the other connecting the lower end of D2 to the lower end of SD2.

The energy which, in FIG. 1, is dissipated by the terminating resistances R1 and R2 is, in FIG. 2 radiated by the second dipole SDI SD2. This, however, does not produce any detrimental side effects because the two dipoles are in mutually perpendicular planes and therefore there is no mutual impedance between them and, moreover, the polarization of the radiation from each is perpendicular to that of the radiation from the other and therefore cannot cause cancellation of one field strength by the other in any direction. The required omni-directional properties, are, therefore, not adversely affected.

Although screened cables are shown at CF 1 and CFZ and the use of such cables is preferred, it is not essential always to screen these cables, for the requirement of substantial nonradiation therefrom can in many cases be conveniently satisfied by putting these connections CF 1, CFZ close enough to the ground or, for the matter of that, burying them in the ground.

I claim:

l. A substantially omni-directional high frequency aerial system comprising a pair of similar mutually perpendicular dipoles each consisting of two coplanar half dipoles sloping downwardly and outwardly from a common upper center; a feeder connected to feed one dipole at the inner upper ends of the halves thereof; and a pair of substantially non-radiating connections each connecting the outer lower end of one or other half of one dipole with the outer lower end of one or other half of the other dipole.

2. An aerial system as claimed in claim 1 wherein the substantially non-radiating connections are constituted by lengths of screened cable. center aerial 3. An aerial system as claimed in claim 1 comprising a central vertical supporting mast carrying a feeder; four mutually perpendicular similar aerial conductors each constituting a half dipole sloping outwardly and downwardly at equal angles from a common upper center on said mast, insulating supports between the upper ends of the aerial conductors and the mast and between the lower ends of said aerial conductors and ground; means connecting the feeder to the upper ends of one pair of co-planar aerial conductors; and two screened connections each between the lower end of a different one of said one pair of aerial conductors and the lower end of one or other of the other pair of aerial conductors. 

1. A substantially omni-directional high frequency aerial system comprising a pair of similar mutually perpendicular dipoles each consisting of two coplanar half dipoles sloping downwardly and outwardly from a common upper center; a feeder connected to feed one dipole at the inner upper ends of the halves thereof; and a pair of substantially non-radiating connections each connecting the outer lower end of one or other half of one dipole with the outer lower end of one or other half of the other dipole.
 2. An aerial system as claimed in claim 1 wherein the substantially non-radiating Connections are constituted by lengths of screened cable. center aerial
 3. An aerial system as claimed in claim 1 comprising a central vertical supporting mast carrying a feeder; four mutually perpendicular similar aerial conductors each constituting a half dipole sloping outwardly and downwardly at equal angles from a common upper center on said mast, insulating supports between the upper ends of the aerial conductors and the mast and between the lower ends of said aerial conductors and ground; means connecting the feeder to the upper ends of one pair of co-planar aerial conductors; and two screened connections each between the lower end of a different one of said one pair of aerial conductors and the lower end of one or other of the other pair of aerial conductors. 